Wonky shapes can be made to roll along a specific path of your choice

Wonky spheres can be sculpted to roll eternally downhill along any possible path, as long as the path repeats. These “trajectoids” could be used to design robots that follow particular routes, or to model how the spin of quantum computer bits, called qubits, will change over time.

Most objects, such as spheres or tyres, will roll down a smooth hill in a straight line. There are some objects that trace curved paths – such as oloids, three-dimensional objects formed from …